1. Field of the Invention
This invention relates to a process for producing a material having a vapor-deposited metallic layer thereon, and also to a process for producing a recording material.
More specifically, the invention relates to a process for producing a sheet-like material having a vapor-deposited metal layer, which comprises forming a metallic layer on a support by vapor deposition using a metal, a metal alloy or a metal compound or a mixture of two or more thereof as an evaporating material, and then vapor depositing an organic material on the metallic layer so as to protect the metallic layer. It also relates to a process for producing a recording material which comprises forming a metallic layer on a support by vapor deposition using a metal, a metal alloy or a metal compound or a mixture of two or more thereof, forming an organic material layer on the metallic layer by vapor deposition, and thereafter forming an organic resin layer on the organic material layer. In particular, the process for producing the recording material is characterized in that after the metallic layer is formed on the support by vapor deposition, additional steps are performed in which an organic material is vapor-deposited on the metallic layer and thereafter an organic resin layer is coated thereon in order to prevent the occurrence of imperfections on the metallic layer, such as pinholes and scratches.
2. Description of the Prior Art
In recent years, techniques for forming vapor-deposited layers of metals, metal alloys or metal compounds, etc. on supports have been actively studied and developed, and have come into wide commercial acceptance. As a result, vapor-deposited layers of aluminum, zinc, silver, copper, cadmium or the like formed by vapor deposition on organic supports such as polyethylene terephthalate, polycarbonate, unplasticized polyvinyl chloride, and cellulose acetates are used in various applications, for example, as gold and silver yarns, decorations, foils, packaging materials, labels, transfer marks, or adhesive tapes. More recently, a wider range of utility has been found in electronic and electrical materials such as condensers and printed circuit boards, and magnetic recording tapes and photographic materials.
The formation of metallic layers by vapor deposition comprises heating a metal, a metal alloy or a metal compound in a vacuum of about 10.sup.-4 torr to about 10.sup.-5 torr, and condensing the resulting vapor on the surface of a support disposed in the vacuum. The metallic layers so formed generally suffer from the serious defect of having a weak mechanical and physical strength and are susceptible to scratching although the degree of the defect varies depending on the kind of the support. In order to avoid such a defect, it is now general practice, particularly in the production of, for example, gold and silver yarns, decorations and packaging materials, to coat a resin layer on the metal layer for protective purposes. The resin layer is formed generally from epoxy resins, polyurethane resins, alkyd resins, melamine resins, phenolic resins and butyral resins. Vapor deposition techniques are well known and are described in Handbook of Thin Film Technology, L. I. Maissel and R. Glang (editors) McGraw-Hill Book Company, (1970). Metallizing of Plastics, H. R. Simonds (editor) Reinhold Publishing Corporation, (1960) etc.
The vapor deposition apparatus widely used for the production of vapor-deposited layers is a so-called semicontinuous-type vapor deposition apparatus in which a roll of a long strip of a support is disposed within a vacuum vessel, continuously delivered from a delivery spindle, and vapor-deposited in a vacuum chamber provided in a space between the above spindle and another spindle for winding up the support. This apparatus includes a support conveying mechanism for delivering the support in a roll form from the spindle, conducting the support to the vacuum chamber, and continuously winding up the vapor-deposited support in a roll form. Such a conveying mechanism usually contains one or more conveyor rollers, and generally the vapor-deposited layer formed on the support in the vacuum chamber contacts with one or more conveyor rollers until the support is wound up in a roll on the spindle. This results in the occurrence of an innumerable number of pinholes and scratches on the vapor-deposited layer, and therefore, this deteriorates the quality of the vapor-deposited layer. When aluminum is used as an evaporating metal and polyethylene terephthalate is used as a support, pinholes having a diameter of about 10 .mu.m to about 50 .mu.m occur to a degree of about 50 to about 100 per cm.sup.2 on the aluminum layer on contact with a single roll even if the conveyor roll is an ordinary one which has a hard chromium plating thereon, which has good surface smoothness and which is free from surface scars (the occurrence of pinholes and scratches depends upon the materials of the conveyor rolls, the surface smoothness thereof and the torque of the conveyor roll). When scars are present on the surface of the conveyor roller, scratches or pinholes corresponding to the scars occur in the metallic layer.
Furthermore, at the time of winding up the vapor-deposited support on a spindle, the vapor-deposited layer contacts the back of the previously wound-up support, and a number of scratches and pinholes occur in the metallic layer as a result of friction due to the fluctuations in tension, that is, the so-called "wind-up tightening".
It is possible to utilize vapor deposition devices which include a conveyor mechanism having one or more conveyor rolls which contact only the back of the support and which do not at all contact the vapor-deposited metallic layer in the conveying path after the formation of the vapor-deposited metallic layer until the support is wound up in roll on a spindle, or a conveyor means which does not utilize a conveyor roll in the conveying passage, although this practice has not come into wide acceptance. Even so, when the support is wound up in a roll form by a spindle, it is impossible to prevent the occurrence of scratches and pinholes in the metallic layer due to "wind-up tightening".
Moreover, in coating an organic resin layer as a protective coating on the vapor-evaporated metallic layer on the support, one or more conveyor rolls which contact the metallic layer and cause a number of pinholes and scratches in the metallic layer are disposed in a conveying passage through which the support having the metallic layer formed thereon which has been wound up in a roll form is conveyed from a spindle in a continuous coating device to a section for coating the organic resin on the support.
As described above, there are many sites which cause pinholes and scratches in the metallic layer in the passage from the vapor deposition section of a semi-continuous type vapor deposition apparatus to the coating section of the continuous coating device, and the number of pinholes and scratches in the metallic layer increases as the support passes these sites successively.
On the other hand, another type of vapor deposition apparatus is widely used in which one or more sheet-like supports are disposed in a vacuum vessel and by vapor deposition a vapor-deposited metallic layer is formed on the surface of the support. Since the support is in a sheet form and not in a roll form, neither conveying nor winding of the support is required. Hence, it is possible to produce a vapor-deposited metallic layer completely free from scratches and having a very low pinhole density. If in a subsequent step of forming an organic resin layer, thereon a high-speed rotary coater called a whirler is utilized, pinholes and scratches do not occur in this step, too. Consequently, it is possible to produce a material having a high quality vapor-deposited metallic layer which is substantially free from pinholes and scratches. This method has the disadvantage of extremely poor productivity, and is quite unsuitable for mass production.
Therefore, difficulties with conventional techniques are encountered in producing a high quality material having a vapor-deposited metallic layer free from imperfections such as pinholes and scratches at low cost on a mass-production basis, and this poses a serious problem both in the utility of the product and in industrial feasibility.
In some applications of gold and silver yarns, decorations and packaging materials, materials having metallic layers with many imperfections such as pinholes or scratches may be used without detrimental effects. However, a protective coating must be formed by coating using a continuous coating device, and great costs must go into its installation. Furthermore, since such materials are produced using the technically different steps of vapor deposition and coating, the production of these materials has the disadvantage of poor efficiency and economic infeasibility.
The recording materials to be produced by the process of this invention means materials consisting basically of a support, a metallic layer formed on the support, and at least a photosensitive resin layer formed on the metal layer, which are classified into image-forming materials in which an image is formed by exposing the material, developing the photosensitive resin layer, and etching away the metallic layer using the resin layer as a resist (that is, a two-bath processing-type image-forming material which requires a developer for the photosensitive resin (or a photoresist) layer and an etching solution for the metal layer), and a mono-bath processing type image-forming material having the same basic structure as the two-bath processing type image-forming material, which, however, requires only one processing solution for developing the photosensitive resin layer and etching the metal layer as described in the specifications of Japanese Patent Application (OPI) Nos. 65927/73, 65928/73, and 139720/75; materials comprising basically a support and at least a metallic layer formed thereon and if desired, a resin layer formed on top of the metal layer, by which recording is performed by irradiating with high density irradiation energy by, for example, a laser or a flash lamp to deform or remove a part of the metallic layer by a thermal method such as melting, evaporation or coagulation, thus providing differences in light transmittance and reflectance, as disclosed in the specifications of Japanese Patent Publications Nos. 2774/67 and 40479/71, and Japanese Patent Application (OPI) Nos. 96716/74 and 19303/73; or materials comprising basically a support, a ferromagnetic metal layer formed thereon, and a resin layer coated on the metallic layer, by which information is recorded using electromagnetic radiation energy, followed, if desired, by development and etching, thereby to provide a difference in the physical condition between the part exposed to the energy and the part which was not exposed to the energy. A method, similar to the process of this invention, can be applied by vapor deposition to the production of magnetic recording materials for recording information by a magnetic method.
The production of the recording material roughly comprises a step of forming a metallic layer on a support by vapor deposition and a step of coating an organic resin layer on the metal layer.
Japanese Patent Publication No. 37435/71 discloses a metal vapor deposition method for vapor depositing a thermoplastic resin on a vapor-deposited metallic layer in the same vacuum system. The purpose of this method is to prevent the peeling of the metallic layer from the support made of a non-polar polyolefin by increasing the adhesion between the support and the metallic layer, and to inhibit the corrosion of the vapor-deposited metallic layer. In order to achieve such purposes, it is essential to adhere a thermoplastic resin in a thickness of about 1 .mu.m to the vapor-deposited metallic layer in the same vacuum system immediately after the vapor deposition of the metallic layer, and the purposes cannot be achieved if the thickness of the resin is less than this specified value. However, thermoplastic resins generally have extremely high vapor pressures when heated, and therefore, this adversely affects the vapor deposition of metal, and with the method disclosed in Japanese Patent Publication No. 37435/71, it is difficult to produce a material having a vapor-deposited metallic layer which has superior properties and a uniform quality. Moreover, no method is suitable for the production of recording materials which includes a step of vapor depositing a layer of an organic material that renders the etching of the metal layer time-consuming at the time of image formation and thus impairs the etchability of the metal layer. The provision of a thermoplastic resin layer having a thickness of about 1 .mu.m as the organic material is quite unsuitable for the production of recording materials.